e scraped off the Archaean continent
and laid on the floor of the sea by its rivers. This meant a very
serious alteration of pressure or weight on the surface of the globe,
and was bound to entail a reaction or restoration of the balance.

The rise of the land and formation of mountains used to be ascribed
mainly to the cooling and shrinking of the globe of the earth. The skin
(crust), it was thought, would become too large for the globe as it
shrank, and would wrinkle outwards, or pucker up into mountain-chains.
The position of our greater mountain-chains sprawling across half the
earth (the Pyrenees to the Himalaya, and the Rocky Mountains to the
Andes), seems to confirm this, but the question of the interior of the
earth is obscure and disputed, and geologists generally conceive the
rise of land and formation of mountains in a different way. They are due
probably to the alteration of pressure on the crust in combination with
the instability of the interior. The floors of the seas would sink still
lower under their colossal burdens, and this would cause some draining
of the land-surface. At the same time the heavy pressure below the seas
and the lessening of pressure over the land would provoke a reaction.
Enormous masses of rock would be forced toward and underneath the
land-surface, bending, crumpling, and upheaving it as if its crust were
but a leather coat. As a result, masses of land would slowly rise above
the plain, to be shaped into hills and valleys by the hand of later
time, and fresh surfaces would be dragged out of the deep, enlarging the
fringes of the primitive continents, to be warped and crumpled in their
turn at the next era of pressure.

In point of geological fact, the story of the earth has been one
prolonged series of changes in the level of land and water, and in their
respective limits. These changes have usually been very gradual, but
they have always entailed changes (in climate, etc. ) of the greatest
significance in the evolution of life. What was the swampy soil of
England in the Carboniferous period is now sometimes thousands of feet
beneath us; and what was the floor of a deep ocean over much of Europe
and Asia at another time is now to be found on the slopes of lofty Alps,
or 20,000 feet above the sea-level in Thibet. Our story of terrestrial
life will be, to a great extent, the story of how animals and plants
changed their structure in the long series of changes which this endless
batt